There are various kinds of motivation for a person to change nationality. But the most potent of all is without doubt that someone wants to be recognised as a member of the society of the country in which they have elected to live.

Japanese people are notoriously narrow-minded when it comes to nationality. For the vast majority of them, somebody who does not look Japanese is a "gaijin". In fact, even people of Japanese descent returning to Japan (the Nikkei), are still considered as non-Japanese.

Just take the examples of Brazilian football players that have immigrated to Japan, obtained Japanese nationality and played for the national team, such as Rui Ramos or Alessandro dos Santos, and are still considered as "gaijin" by the Japanese. They are famous and most people know they have the Japanese nationality. Santos is even partly of Japanese descent. Yet, they were not born in Japan or pure-blood Japanese parents, raised in Japanese with the Japanese education system, so in a normal Japanese's mind, such a person will always be a "gaijin".

Arudo Debito is another good example of how a non-Japanese looking person taking one Japanese citizenship, will always be treated as a foreigner, and even refused entry to some places reserved to Japanese, even after showing their passport proving that they are Japanese. Paper nationality hardly counts to a Japanese. To be Japanese, you must look Japanese, be born and raised in Japan and speak Japanese like a native.

Just speaking Japanese like a native, or knowing more about Japanese culture and society than most Japanese will not make you any better accepted. I have seen myself, as a permanent resident married to a Japanese, that anyone that doesn't know me will automatically assume that I do not speak Japanese and cannot do any of the cultural stuff thought of as typically Japanese (even when they are not). Some people will say it is normal, as somebody who doesn't know me cannot possibly know how long I have been in Japan and what is my status. But many of those who know still treat me as if I were a freshly arrived tourist, or could never possibly get used to Japanese food, chopsticsk and sleeping on a futon, just because I am a foreigner.

With this kind of mindset, it is hard, very hard indeed, to be accepted as part of the group. The Japanese are exclusive. They typically pre-judge people on their appearance, which blow up all hopes to be ever accepted as "one of them". If even a house-hold name like Santos is still considered as an "outsider" after playing at the Japan-Korea World Cup on the Japanese team, then there is no chance for a less illustrious citizen to ever be accepted by more than a few close acquaintances.

So what is the point of becoming naturalised Japanese ? This should be one of the most disastrous action one could ever take in their citizen's life. As Japan does not accept dual citizenship, it would effectively mean having a paper nationality that most people in the society do not recognise, stay out of the group in the eyes of the group, and be treated as a foreigner in one's birth country (for visas, work, etc.). In other words, such a person would lose all feeling of belonging to a particular society, which could be one of the worst thing a human may have to endure psychologically.